In filling machines the capsules, supplied closed by the producer, are orientated with their lid upwards, the capsule lids and bases are separated from each other, the bases are filled with a given quantity of pulverulent substance, the filled bases and the lids are again fitted together, and the filled and closed capsules are discharged. These operations are carried out in stations comprising the appropriate devices.
One of the critical operations in such machines is clearly the pulverulent substance dispensing, the accuracy of which can be influenced by the nature of the powder (for example its fluidity) and also by the environmental conditions under which the operation takes place (for example humidity and temperature).
In the machines described in U.S. Pat. No. 3,242,638, the problem of correct dispensing is confronted by choosing the powder formulation to give it constant characteristics, and by operating in a controlled environment.
The problem of correct dispensing is however different for other types of machines which can also operate or have to operate in uncontrolled environments, with limited production and with pulverulent products of differing characteristics, for which for obvious economical reasons the formulation cannot be adjusted.
Dispensing devices of different types have already been proposed with the intention of obtaining adequately accurate dispensing even in the case of limited production machines for operating in uncontrolled environments with pulverulent products of various characteristics.
Hetice for example, U.S. Pat. No. 1,876,813 comprises a continuously operated vertical screw which forces the pulverulent material through an exit aperture below which the capsule base is situated. This known device is simple, but results in material spillages (losses) even when no base is situated under the aperture and is also inaccurate as the screw throughput depends to a substantial extent on the powder level in the hopper in which the screw is located.
U.S. Pat. No. 1,993,716 comprises a hopper lowerly provided with two side pockets into which the powder is fed by a rotary star member. A piston in each pocket thrusts the powder into an underlying capsule base. Again in this known device the amount dispensed depends on the powder level in the hopper.
PCT W096/11658 comprises a hopper, an eccentric rotor in said hopper, a discharge aperture in said hopper, and a discharge aperture closable by a slide and provided in the hopper base. When in one position, this slide forms the movable wall of a chamber in which the powder arrives from said aperture, while when in another position it forms with the fixed part a hole into which the powder is compacted and within which a piston operates to discharge the powder into the underlying capsule base either directly or indirectly. This known device is difficult to set to provide given quantities of product as the slide position has to be regulated.